This invention relates generally as indicated to a modular emergency stop device and system and more particularly to an emergency stop device and system having a switch unit and a control unit that may be coupled/uncoupled in a modular manner.
A machine is typically powered by an electrical power source and typically has an on/off switch for use during normal operating conditions. For safety reasons, a machine will usually also include an emergency stop device for terminating electrical power to the machine in an emergency situation. While the design of an emergency stop device may vary greatly, the device will generally include a switch which converts from a normal state to an emergency state when an emergency stop is necessary and a controller which controls the power source for the motor or machine. The switch and controller typically are enclosed in a housing or casing to protect them against weather, dust, explosive situations, or other hazards presented by the environment of the particular machine.
In a more sophisticated emergency stop device, the switch will include a circuit board including, among other things, a series of contacts that are either normally closed or normally open contacts. The controller in a sophisticated emergency stop device will usually include a microprocessor for appropriating controlling the machine""s power source in an emergency situation. The switch, and specifically its contacts, are usually considered component most vulnerable to damage and deterioration. However, in view of the criticality of the switch in the operation of the emergency stop device, a faulty contact must be replaced or else the machine will not run until the relays are replaced. For this same reason, the ability to periodically inspect and/or test switch components could be a very important part of a preventive maintenance plan but such inspection/testing is not always possible or at least not practical.
Accordingly, the inventor appreciated that a need remains for an emergency stop device which allows efficient and convenient replacement, inspection and/or testing of the switch components.
The present invention provides an emergency stop device wherein the switch and the controller are contained in separate modular units. This modular construction allows the switch to be conveniently removed from the controller and then replaced, inspected and/or tested.
More particularly, the present invention provides a modular emergency stop device comprising a switch unit and a control unit. The switch unit includes a switch which converts from a normal state to an emergency state when an emergency stop is necessary and a housing for the switch. The control unit includes a controller which controls a power source for a machine and a housing for the controller. The switch unit""s housing and the control unit""s housing are adapted to be selectively coupled/uncoupled relative to each other. When the housings are coupled together, the switch is operably coupled to the controller, whereby the controller may appropriately control the machine""s power source when the switch is converted to the emergency state. Preferably, the housings include a quick-release coupling arrangement therebetween.
The switch may comprise a circuit arrangement necessary to convert the switch to the emergency state if an emergency stop is necessary. The circuit may include, among other things, contact pins which are usually the component most vulnerable to damage and deterioration in the emergency stop device. To replace the switch, the switch unit""s housing is uncoupled from the control unit""s housing to remove the switch unit and a new switch unit is coupled to the controller""s housing. Likewise, to test the switch, the switch unit""s housing is uncoupled from the control unit""s housing to remove the switch unit, the uncoupled switch unit is tested, and the tested switch unit is recoupled to the controller unit if testing reveals that the switch is still acceptable. Preferably, the switch unit""s housing includes a plurality of housing sections latched together to form a casing for the switch and/or the control unit""s housing includes a plurality of housing sections latched together to form a casing for the controller. For example, the switch""s housing may include a front housing section and rear housing section and the controller""s housing may include a front housing section and a rear housing section. In this manner, the switch and/or controller may be easily accessed from its respective housing by unlatching the housing sections.
An emergency stop system may be compiled by interconnecting directly (or substantially directly) a plurality of modular emergency stop devices via connectors which eliminates field wiring therebetween and improves system reliability. Additionally or alternatively, diagnostics or other functions could be provided by the additional control units. To this end, each of the controllers would preferably include a network interconnection base and the control units"" housings would each include a window for this base to facilitate the interconnection of various modules.
As indicated above, the modular coupling between the switch unit and the control unit provides many advantages over traditional single unit emergency stop devices in the areas of replacement, testing, and/or repair. A further manufacturing advantage is that the controller may be programmed to be compatible with a plurality of different switch units for different machines and/or different emergency stop conditions. The appropriate type of switch unit for the machine and/or the desired emergency stop conditions could then be selected and the controller provided with the selected switch unit.
These and other features of the invention are fully described and particularly pointed out in the claims. The following descriptive annexed drawings set forth in detail certain illustrative embodiments, these embodiments being indicative of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.